Repairing Crystal Earpieces

If you make crystal radios, you’ve probably got a few crystal earpieces. The name similarity is a bit coincidental. The crystal in a crystal radio was a rectifier (most often, these days, a germanium diode, which is, a type of crystal). The crystal in a crystal earpiece is a piezoelectric sound transducer.

Back in the 1960s, these were fairly common in cheap transistor radios and hearing aids. Their sound fidelity isn’t very good, but they are very sensitive and have a fairly high impedance, and that’s why they are good for crystal radios.

[Steve1001] had a few of these inexpensive earpieces that either didn’t work or had low sound output. He found the root cause was usually a simple problem and shares how to fix them without much trouble.

The root cause of failure in these is typically a poor connection on a piece of copper inside the device. [Steve1001] disassembles the unit with a knife, drills a new hole, and adds an additional wire. The process isn’t complicated but seeing how its done might keep you from tearing up one in the disassembly attempt.

Finding a local source for crystal earpieces might be tough, but piezo speakers are common on things that make beeps like motherboards or microwave ovens. Hackaday’s own [Steven Dufresne] shows how to convert one into a workable crystal earpiece in a video below. We’ve seen him make other homemade versions, too. Of course, big time crystal radios have amplifiers and can use conventional speakers and earphones.

Heard a ceramic laminated diaphragm (ceramic on both sides of the plate) give out a decent tweet response. Whereas both low end and high end audio have compression tweeters (and compression mid-horns for the PA)

Even a plain cheap ceramic disc can produce some decent Mid-HiFi quality sound if: driven at the right voltage, frequency and mounted in such a way as to allow the sound to direct in to the air (Rigid connection)

Some handhelds at work use these and they produce quite a decent mid-bass output for music. Not bad for a multilayer-seal evacuated chamber mounted ceramic disc

“The name similarity is a bit coincidental. The crystal in a crystal radio was a rectifier (most often, these days, a germanium diode, which is, a type of crystal). The crystal in a crystal earpiece is a piezoelectric sound transducer.”

It’s almost as if crystal describes the particular form of a substance, rather than what the substance actually is.

Heh, imagine if ppl were that stupid you could actually use it as a TV plot device, where a sort of antihero pretends a crystal explosive he made is a crystallised drug and blows the bad guys up with it when they think they’re doing a drug deal or something.

Interesting idea about how to repair them; I’d not known about that. Once the diaphragm and the terminals are exposed, you could probably make some quick tests with an ohmmeter to see if the connection to the diaphragm is actually a problem, or tack solder a bit of resistor lead to the back and bend it around to the diaphragm to see if that does improve things, before drilling holes.